Gene Flow
Movement of individuals between populations provides another possible source of diversity. emigration may result in the lose of alleles but immigration may result in the addition of new alleles into the population.
Sometimes the variation introduced into a population is not beneficial. An inherited anaemic disease, thalassaemia, is common among people living along the Mediterranean coast, particularly among people of Greek origin. As people from this part of the world migrated to Australia, they brought with them the thalassaemia allele. Although this trait is recessive and requires two heterozygous parents to contribute it for their offspring to express it, there is an increasing number of people within the Australian population with this disease.
In other cases, the introduction of a genetic trait into a population may increase the chances of survival of individuals with the trait. This new variation may contribute to increasing the fitness of the population to the current or future environment.
Sometimes the variation introduced into a population is not beneficial. An inherited anaemic disease, thalassaemia, is common among people living along the Mediterranean coast, particularly among people of Greek origin. As people from this part of the world migrated to Australia, they brought with them the thalassaemia allele. Although this trait is recessive and requires two heterozygous parents to contribute it for their offspring to express it, there is an increasing number of people within the Australian population with this disease.
In other cases, the introduction of a genetic trait into a population may increase the chances of survival of individuals with the trait. This new variation may contribute to increasing the fitness of the population to the current or future environment.